On January 14, 1803, the Governor of Indiana Territory, William Henry Harrison, issued a similar proclamation defining the boundaries as beginning at a point where an east and west line passing through the southernmost extreme of Lake Michigan would intersect a north and south line, passing through the westernmost extreme of the lake, then north to the territorial boundary, then along said boundary line to a point where an east and west line passing through the southerly extreme of Lake Michigan would intersect the same, then along this last mentioned line to the place of beginning. This boundary would include Chicago, Illinois and a sizable strip of Wisconsin along Lake Michigan.[7]

According to the U.S. Census Bureau, the county has a total area of 673 square miles (1,740 km2), of which 612 square miles (1,590 km2) is land and 61 square miles (160 km2) (9.0%) is water.[8] Its water area includes parts of the Detroit River and Lake St. Clair.

The eastern (and sometimes southern) boundary is a water boundary in the Detroit River and Lake St. Clair with Essex County, Ontario. Automotive traffic crosses this boundary at the Detroit-Windsor Tunnel and the Ambassador Bridge. Due to the southwestern course of the river, this small portion of Canada actually lies to the south of Wayne County. The southern communities of the county are usually referred to as "Downriver", in reference to their location downstream of downtown Detroit.

I-75 through the Downriver communities, then through the southwest-side neighborhoods of Detroit and serves as the northern border of Downtown Detroit as the Fisher Freeway. It then turns away from the Fisher onto the Chrysler Freeway at a complex interchange with I-375 and an unnumbered extension which connects with M-3, then follows M-1, which is less than a mile away through the remainder of Detroit, connecting eastern Wayne County to Toledo and Flint to the south and north respectively. It runs non-stop to the Sault Ste. Marie International Bridge to the north and to Florida to the south.

I-94 runs east-west through the central parts of Wayne County, connecting it to Port Huron eastbound and Chicago westbound. To the west it provides an uninterrupted route as far as Montana and connects to the northern side of the Detroit Metro Airport. In Detroit it is known as the Edsel Ford Freeway.

I-96 has its eastern terminus in the county, in Detroit. It follows Grand River Avenue until the city's northwest side, there it turns due west to I-275, where it turns north to concurrent with I-275. West of Detroit to I-275 it is known as the Jeffries Freeway; in Detroit it is the Rosa Parks Memorial Highway, but it is sometimes still known as the Jeffries.

I-375 is the nation's shortest Interstate Highway to be signed. However some highways are shorter but are not signed at all. It serves as the eastern boundary of Downtown Detroit and is a southern extension of the Chrysler Freeway.

US 12 has its eastern terminus in Downtown Detroit at Cass Avenue. From there it travels through the west side of Detroit and through Dearborn and other points west and is a useful alternative to I-94. Locally it is known as Michigan Avenue.

US 24 traverses through Downriver and the far west sides of Dearborn and Detroit and is a useful alternative to I-75. Locally it is known as Telegraph Road.

US 10 entered the county by two ways. Initially it was via Woodward Avenue but when the Lodge Freeway was completed U.S. Route 10 was relocated onto it; the Woodward route became M-1. Later the existing highway was truncated in Bay City and M-10 replaced it on the Lodge.

US 25 was the designated name for Dix-Toledo Highway in Downriver and Fort Street and Gratiot Avenue in Detroit. The construction of I-75 resulted in the truncation of U.S. Route 25 to Cincinnati.

US 112 followed Michigan Avenue out of Downtown Detroit and out of Wayne County. Is now a routing of U.S. Route 12.

M-1 has its southern terminus in Downtown Detroit at Adams Street. It travels through Midtown Detroit and New Center and through Highland Park. It serves as an alternative to I-75 and M-10. Locally known as Woodward Avenue. M-1 was a result of US-10 being redesignated to the Lodge Freeway.

M-3 has its southern terminus in Downtown Detroit at Randolph and Jefferson Avenue. It proceeds northeasterly through Detroit's northeast side and beyond towards Mount Clemens and points further north. Locally known as Gratiot Avenue. M-3 was the result of the removal of US-25 from Michigan.

M-5 begins at the northern intersection with I-96 on Detroit's northwest side and follows Grand River Avenue out of the county.

M-8 runs from I-96 to Conant Street in Detroit, passing through Highland Park. The freeway portion is known as the Davison Freeway.

M-10 starts at the same intersection where M-3 starts in Downtown Detroit and travels further into the city on the Lodge Freeway and connects it to Southfield.

Dixie Highway ran through Wayne County as early as 1915. Back then it was one of the only routes that connected the county to the Southern United States. Today there are no traces of the old highway in the county.

Coleman A. Young International Airport is also known as the Detroit City Airport, which is not to be confused with the larger and nearby Detroit Metro Airport. It is located just a short drive from Downtown Detroit along M-3. It also has two runways and no scheduled flights, although it has been attempted in the past.

There were 702,749 households out of which 33.1% had children under the age of 18 living with them, 37.4% were husband and wife families, 20.7% had a female householder with no husband present, 35.9% were non-families, and 30.7% were made up of individuals. The average household size was 2.56 and the average family size was 3.22.

In the county the population was spread out with 25.4% under age of 18, 9.7% from 18 to 24, 25.5% from 25 to 44, 26.8% from 45 to 64, and 12.7% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 92.4 males. For every 100 females age 18 and over, there were 88.7 males.

The 2010 American Community Survey 1-year estimate[13] indicates the median income for a household in the county was $39,408 and the median income for a family was $49,176. Males had a median income of $26,823 versus $17,744 for females. The per capita income for the county was $20,948. About 18.6% of families and 23.7% of the population were below the poverty line, including 34.8% of those under the age 18 and 11.7% of those age 65 or over.

As of 2001, of the U.S. counties, Wayne County has the 51st largest Asian population.[15]

Wayne County is Michigan's first "charter county", with a home rule charter setting up its structures within limits set in state law and constitution. Most Michigan county governments are structured according to state law, without a locally adopted charter. The city is governed pursuant to the Home Rule Charter of Wayne County, Michigan, and the Wayne County Code is the codification of Wayne County's local ordinances. Unless a violation of the code or other ordinance is specifically designated as a municipal civil infraction (or unless expressly otherwise required by applicable state or federal laws), the violation is a misdemeanor.[16]

The county government operates the jail, maintains rural roads, keeps files of deeds and mortgages, maintains vital records for all areas except Detroit, administers public health regulations, and participates with the state in the provision of welfare and other social services. Most other local government functions – police and fire, building and zoning, tax assessment, street maintenance, etc. – are the responsibility of individual cities and townships.

The Wayne County Jail Division operates The Andrew C. Baird Detention Facility in Downtown Detroit, The Old Wayne County Jail in Downtown Detroit, and The William Dickerson Detention Facility in Hamtramck.[19]